The enzyme adenylosuccinate synthase carries out the reaction of IMP to S-AMP in a 2 step mechanism,[1] requiring the input of energy from a phosphoanhydride bond from the hydrolysis of guanosine triphosphate (GTP)[2] first, followed by the addition of aspartate.

This reaction needs Mg2+,[3] and is competitively inhibited by the subsequent product AMP[3] in a negative feedback mechanism.

[4] GTP, the product of another pathway from IMP, is used instead of adenosine triphosphate (ATP) as the phosphate source.

The enzyme adenylosuccinate lyase carries out the reaction removing the carbon skeleton from S-AMP attached from aspartate, forming AMP and fumarate.

[4] The pathway from IMP to AMP is present across various prokaryotes and eukaryotes, and is linked to various diseases.